Cooking for one or two is really no problem, although if you don't have room in the freezer for leftovers could be problematical.
On the rare occasion I buy standing rib roast (prime rib, if you will) I get a 5-7 pound roast, bone-in, not boneless! Those roasted rib bones are great for making a nice rich beef stock! So this is for future reference
I've been using this same method since 1976:
5-7 lb. bone-in standing rib roast
3-4 cloves garlic, cut into slivers
salt & pepper
Preheat oven to 500F. Trim most of the fat from the roast (but not all). Cut small slits all over the top and insert slivers of garlic deep into the flesh. Pat salt, pepper and thyme onto the beef. Place the roast, rib-side down, in a roasting pan. Place roast in oven and immediately turn the heat down to 375F. Roast for 1 hour. DO NOT OPEN THE OVEN DOOR.
Turn the oven completely off
. Again, do NOT open the oven door. Let the roast stand in the oven for 2 hours. Turn the oven on again at 375F. DON'T OPEN THE DOOR!
Roast 40 minutes for rare in the middle roast, 55 minutes for medium. (blasphemy!) Remove from oven. Let stand 10 minutes (loosely tented with foil) before slicing. Slice in 1" thick slices using the rib bones at the bottom as a guide. Cut sideways across the bones to release the slices. Strain the pan drippings and stir in a little red wine and serve 'au jus'.
Save the bones for making stock, or you can use them to make "prime rib BBQ" (had that in a restaurant in Texas once, came home and took the rib bones out of the freezer and put them on the grill.)